Machines and methods for uniting multiple layers of work



p 1959 M. MAESER ET AL 2,903,983

MACHINES AND METHODS FOR UNITING MULTIPLE LAYERS OF WORK Filed June 30, 1955 2 Sheets-$heet 1 p 1959 M. MAESER ET AL 2,903,983

MACHINES AND METHODS FOR UNITING MULTIPLE LAYERS OF WORK Filed June 30, 1955 2 Sheets-Sheet 2 If; I nw inventors: M/zfh Maesr Freden c/v 5. W/ars .By (he/r" flforney United States Patent O MACHINES AND IVIETHODS FOR UNITING MULTIPLE LAYERS OF WORK Mieth Maeser and Frederick S. Sillars, Beverly, Mass, assignors to United Shoe Machinery Corporation, Flemington, N.J., a corporation of New Jersey Application June 30, 1955, Serial No. 519,136 8 Claims. (Cl. 112-43) This invention relates to machines and methods for uniting multiple layers of work composed of relatively dense, nonabsorbent materials with adhesive fastenings wherein the work is fed with a step-by-step movement, and more particularly the invention includes improvements in the art of high velocity adhesive fastening leather shoe parts, such as soles, welts and uppers, said machine being similar to that disclosed in applications for United States Letters Patent, Serial No. 359,982, filed June 1, 1953, in the names of Frederick S. Sillars, one of the present inventors, and Henry C. Pavia'n, deceased; and Serial No. 358,809, filed June 1, 1953, in the name of Frederick S. Sillars, now Patent No. 2,778,530, granted January 22, 1957.

The prior apparatus disclosed in the application and patent above noted is provided with an adhesive impeller connected to a nozzle for squirting thermoplastic adhesive in a high velocity jet to cause it to penetrate to an interface between layers of leather or other fibrous work presented to the nozzle by an operator. The prior apparatus has many advantages and features of utility where multiple layers of work are to be united by fastenings inserted at random along the outer surface of the work.

It is a purpose of the present invention to provide a machine capable of inserting fastenings by high velocity adhesive jet apparatus where it is found desirable to guide them in a line of predetermined contour in the manner of connected stitches with a lock stitch or other form of sewing machine. In actual practice it has been found effective to employ the prior high velocity adhesive in the operation of a lock stitch shoe sewing machine of the type disclosed in United States Letters Patent No. 2,271,611, granted February 3, 1942, in the names of Ashworth et al. In certain of its aspects, however, the invention is intended to combine the prior apparatus with the machine of the Ashworth et al. patent, either in the use of the machine to insert an adhesively reinforced lock stitch seam or, as a step feed, high velocity adhesive jet machine for inserting a line of fastenings without thread.

In accordance with the purposes above referred to, the machine embodying the invention is intended for operation upon two or more layers of dense fibrous work and is provided with fastener forming, work clamping and step-by-step feeding devices including an adhesive impeller, a connected nozzle directed against the work, an actuating mechanism including a spring-actuated hammer raised during operation of said mechanism and released with an explosive blow for causing the impeller to squirt adhesive from the nozzle with such high velocity that the adhesive will continue in motion by its own inertia into the work to an interface between the work layers, in which machine there are arranged driving connections between the impeller mechanism and the feeding devices for actuating the impeller once for each step of the feeding devices. Such action is distinguished from that occurring when adhesive is forced by pressure only into the work. When the machine is operated exclusively to insert high velocity adhesive fastenings a needle or an awl is not required, the adhesive being injected into the work and forming its own perforation by reason of its acquired velocity rather than by its pressure. When a thread seam is inserted the adhesive injecting nozzle is spaced from the point of operation of the needle and awl a sufficient distance along the line of a seam inserted to cause the adhesive to be squirted in line with a perforation containing the sewing thread already squeezed into the perforation and usually containing a wax or other lubricant, the adhesive then acting not only to bond the layers of work but also to reinforce and strengthen the portions of the thread running through the perforation, as well as to bond the thread securely to the work in spite of the frangible nature of wax at room temperatures.

Many advantages result from the use of the high velocity adhesive jet apparatus in a sewing machine, such as a capability of easy adjustment for the velocity and quantity of adhesive charge in the jet, in which all of the adhesive employed may be applied to the thread within the perforation without any appreciable accumulations at the outer faces of the work, the thread within the perforation and the material of the work being more intimately impregmated with the adhesive than has ever been possible with prior external applications of adhesive to completed stitches.

In accordance with the improved method of making the seam, successive charges of high velocity adhesive are concentrated at an interface between superimposed layers of work both in the thread and in the dense material of the work, which charges migrate between the layers to a Sufiicient degree that conjunctions occur between charges, thus providing a continuous line of fastening. In adapting this method to the sewing art a series of perforations passing through one layer of multiple layer work, intersecting the interface between the layers and extending part way into another layer is formed to receive loops of thread compacted by the compression of the work material in a conventional manner and the high velocity adhesive is squirted into the interstices of the thread, filling the thread in the perforations and the materials of the perforation side walls solidly while bonding the thread to the side walls of the perforations in a new and unexpectedly effective manner and eventually providing a continuous reinforcing connection of hardened cement running between the surfaces and connecting the perforations along the interface between layers.

Other features of the invention consist in the devices, combinations, arrangements of parts, sequences of steps and procedures hereinafter described and claimed, the advantages of which will readily be understood from the following detail description taken in connection with the accompanying drawings, in which:

Fig. 1 is a view in left side elevation, partly broken away and in section, of a sewing machine embodying the features of the present invention;

Fig. 2 is an enlarged sectional detail view looking from the front of the machine at the point of operation of the fastening devices; and

Fig. 3 is a fragmentary view of a portion of an adhesive charge holder and impeller for the machine.

In the use of the machine disclosed in the Sillars patent above identified it has been considered sufficient to insert fastenings at widely separated locations along the area of a layer of dense material such as leather or other fibrous work to be attached to another dense layer or part. It has been found, however, according to the present invention that there are certain advantages in inserting fastenings at closely spaced intervals when attaching a single layer of work to another part or layer. As the machine is operated with close interval spacing and hot-melt adhesive, a charge is injected at high velocity through one layer of work,

each charge being accelerated by an explosive hammer blow to a velocity higher than that required to cause it to continue in motion by its own inertia into a dense work piece. The adhesive charge is dispersed at the interface between that and another layer of work where the charge loses its inertia, spreads out and eventually is transformed to hardened cement. When a second closely adjacent charge is injected it has been found that the second charge migrates between the layers and forms a conjunction with the first charge resulting in a continuous line bond of hardened cement between charges. When a continuous line bond is produced between the layers by charges spaced uniform distances apart a stronger connection is provided with the additional benefit of a fluid tight joint between the layers.

When high velocity adhesive is combined with thread stitching the thread and the work material surrounding each stitch perforation in a seam are more thoroughly impregnated with adhesive than in prior methods of combined adhesive and thread attachment. Also squirting adhesive by high velocity injection into a perforation containing thread is less likely to cause accumulations on the surface of the work and is more readily susceptible to accurate and effectively uniform control. For instance, where the completed stitches of a thread seam are injected with high velocity hot-melt adhesive, the velocity may be controlled to enter into the material immediately surrounding each perforation to a uniform predetermined depth only.

As the inertia of an adhesive charge is absorbed by the thread within and about the perforation in the layers of a work piece operated upon, it forms a dam behind which trailing portions of the charge accumulate. The depth of accumulation within the work piece itself is more or less dependent upon the resistance offered to its passage through the perforation by the thread which is compacted therein and the velocity with which it is injected, the ad hesive following the lines of least resistance. If the dam at the forefront of the injected charge of adhesive is formed beyond an interface between two layers of the work, then the charge will migrate along the interface to an extent depending upon the quantity of adhesive in the charge and the degree to which the thread is compacted. With the use of high velocity adhesive in a thread seam of a given character and thread compaction it is possible to cause sufficient migration Without the presence of any accumulation at the outer surface of the work piece merely by limiting the quantity of the charge to the amount required. Thus, there is no excess of adhesive to stiffen a seam unduly against flexure where two layers are being attached and undesirable accumulations of adhesive on the work piece or on the operating devices in the machine are avoided.

Referring more particularly to Fig. 2 of the drawings, a seam inserted by the practice of the method and by the use of the preferred machine construction is illustrated. The work operated upon is composed of multiple superimposed work layers shown for-the sake of simplicity as consisting of two parts 4 and 6, comprising the leather sole and welt, respectively, of a shoe. The stitches are inserted by the usual devices acting to form a series of perforations passing through the work layers 4 and 6 and to carry through the perforations and across an outer surface of the work successively formed loops of a continuous length of machine or needle thread 8. A similar loop of a continuous length of locking thread 10 is inserted into and interlocked with each projecting loop of needle thread and is drawn tightly into the work by a loop of needle thread to form a conventional lock stitch seam, the points of interlocking engagement between the loops of thread being located approximately half way between the surfaces of the outsole 4. After each stitch is formed and tightened to bring the point of interlocking engagement between the threads into the outsole the threads are squeezed compactly into the perforations where they are held frictionally by the inner walls of the perforations. Then a charge of high velocity hot-melt adhesive is squirted into the stitch perforation. The velocity and quantity of adhesive charge is so determined that it continues in motion by its own inertia through each perforation and to some extent through the material of the work about the perforation in the outsole 4 to an interface 12 between the outsole and welt 6, the forepart or dam of the charge being carried beyond the points where the threads 8 and 10 are interlocked and slightly beyond the interface between the layers. As the velocity of the charge is reduced by the resistance offered in filtering through the interstices of the threads and the material of the work it loses a substantial quantity of its heat, especially along the area of the advancing front at the forepart of the charge. The reduction in velocity and cooling and solidifying action suddenly becomes critical and a dam 14 of cement is formed having a more or less solid convex area behind which the still fluent remainder of the adhesive charge piles up and enlarges behind the forepart of the charge. The advancing adhesive charge bringing with it the remainder of the heat initially contained therein exerts a pressure on the solid darn 14, especially along the sides of a perforation, whereupon a portion of the charge spreads out to a substantial degree and migrates laterally along the adjacent inner surfaces of the layers formed by the outsole and welt, being reduced in velocity and thereby confined within the interface surfaces of the work. The quantity of the charge, the temperature to which it is raised and the velocity with which it is initially squirted are so adjusted that the confining side pressure produced by the sides of the perforation and the interface surfaces causes the charge to migrate more than half way from the perforation between layers toward an adjacent charge, thus forming a conjunction with the previous charge.

The completed seam constructed in this way appears to be similar in all respects to one having no adhesive reinforcement but has far greater strength and durability. The velocity with which the adhesive is carried into the perforation is sufiicient to prevent any external accumulation at the side of the work piece from which the adhesive is squirted and the darn. 14 forms a barrier for stopping the remainder of the adhesive charge to prevent accumulations at the other side of the work piece. In this way the effect of the high velocity charge is concentrated along the area about a limited length of a perforation into which it is squirted, the thread being bonded to the sides of the perforations by a multiplicity of minute branches running from the bulk of each adhesive charge and having a fluid tight reinforcing connection running between the work layers. These results are obtained by relatively simple adaptation of the apparatus, disclosed in the Sillars patent, to a lock stitch outsole stitching machine similar to that disclosed in the Ashworth et al. patent. In certain of its aspects, however, the invention is not limited to the art of sewing with a thread seam but may be utilized to advantage merely in combining a high velocity adhesive fastener forming apparatus with a known elementary form of work clamping and step-bystep feeding device with no work penetrating instrument.

The work clamping and step-by-step feeding devices of the illustrated machine include a work support 16, and a cooperating work clamping and releasing presser foot 18. The presser foot 18 is secured to a lever 20 fulcrumed on a horizontal pin 22 supported in a feed carriage 24. The feed carriage 24 is mounted for horizontal swinging movement and acts with the work support 16 and the presser foot 18 to clamp and feed the work and also to release the work and back feed the distance between the stitches to be inserted. To prevent the work from moving with the work support and presser foot while the feeding devices are being back fed, it is engaged by a curved work piercing awl 26 (Fig. 2) mounted for oscillation about a supporting pin engaged at its opposite ends with a pair of adjusting screws, one of which is illustrated at 28 (Fig. 1). Also mounted for oscillation on the awl supporting pin is a curved hook needle 30 acting with a shuttle 32, a loop spreader 34 and other stitch forming devices in the machine to carry loops of needle thread 8 through perforations in the work which are formed by the awl and to interlock loops of locking thread with each needle loop so that as a needle loop is tightened it draws a loop of locking thread into the work in a conventional manner. For actuating the stitch forming devices they are connected with mechanisms driven by a main sewing shaft 36. As more fully disclosed in the Ashworth et al. patent, the sewing shaft 36 is mounted for rotation and the stitch forming devices for actuation in a sewing frame 38.

The high velocity adhesive apparatus comprises an impeller supported directly on the sewing frame 38 with its outlet substantially in vertical alinement with and above the point of operation of the stitch forming devices. For this purpose the sewing frame 38 is formed with a horizontal face engaged by the underside of an impeller supporting frame 40 bolted to it. The impeller frame has a lower shelf portion to which is attached a bracket 42 provided with bearings for a horizontal impeller actuating crank shaft 44, the crank of which passes through a connecting rod 46 pivoted to a walking beam 48 of channel section pinned to a fulcrum shaft 50. The fulcrum shaft 50 is supported in bearings formed in flanges of a block 52. The bearing block 52 is mounted above the level of the shaft bracket 42 by a riser projecting from the horizontal shelf of the frame 40 and a raised step extending forwardly from the riser, the block 52 being bolted to the horizontal step. The walking beam 48 is connected to the impeller by means of hooks swinging between the flanges of the beam 43, one of which hooks is illustrated at 54, the hooks forming a releasable connection with the impeller. The shaft 50 to which the walking beam is pinned also has rotatable on it an arm 56 for actuating a valve to limit the quantity of adhesive acted upon by the impeller as each charge is squirted at the work.

The impeller includes a charge forming pump (not shown), a combined charge measuring valve and injecting piston 58. For actuating the impeller, mechanism is provided including a vertical reciprocating hammer 60 slidable in a slotted tube 62 and a spring 64 compressed within the tube 62 between the hammer 60 and a cap 63 at the upper end of the tube. The tube 62 is secured to the raised step of the adhesive frame 40 in alignment with the piston 58, so that when the hammer is raised and released the spring 64 expands and causes the hammer to strike the piston 58 with explosive force. For this purpose the hooks 54 engage the ends of a pin 66 passing through the upper end of the hammer and through the slots in the tube 62, the pin being released from the hooks during their upward movement. To permit the hooks to swing they are provided with a pair of pins 68 rotatable in flanges of the beam 48. During upward movement of the hooks 54, they are swung away from the pin 66 to release it by engagement with a set screw 72 of a cross flange 70 connected between the hooks, the set screw being mounted on a clamp ring 74 carried by the tube 62. Fig. l of the drawings shows the position of the parts just after the impeller has been actuated to squirt a charge into the work. For a better understanding of the construction and mode of operation of the impeller reference may be had to the application and patent above noted.

In the machine of the prior application and patent the impeller actuating shaft is driven from a continuously rotating driver through a single revolution clutch mounted on the impeller actuating shaft.

In the construction of the present machine, it is unnecessary to employ a single revolution clutch, the adhesive impeller being actuated in unison with the work feeding and stitch forming devices. Accordingly, a charge of adhesive is squirted into the work after each stitch formed by the stitch forming devices is completed regard less of the speed of sewing operations. Thus, while sewing a shoe it is possible to run the machine more slowly around diflicult portions of a seam connecting the shoe parts and to increase the speed of sewing along less difli cult parts without in any way interfering with the operation of the adhesive apparatus. For this purpose properly timed direct driving connections are provided between the sewing machine and the adhesive apparatus.

The timed connections between the sewing machine and the adhesive apparatus required for successful sewing operations include a simple form of sprocket and chain drive. To the machine sewing shaft 36 is keyed a sprocket 76 under which passes a conventional roller chain 78, also passing over a sprocket 80 keyed to the shaft 44 of the adhesive impeller. The diameters of the sprockets 76 and 80 provide a one-to-one driving ratio between the two shafts. The timed relation of the shafts causes a charge of adhesive to be squirted into the work after each stitch is completed, the work having been moved a stitch length away from the operating point in the sewing machine. To transmit each high velocity charge of adhesive from the outlet of the impeller to the proper position in the sewing machine for successfully squirting adhesive into the work, the piston 58 is mounted for sliding and rotating movement in a closely fitting charge holder 82 secured beneath the raised step of the frame 40. The charge holder has a screw connection with a fixture 84. Connected to the fixture 84 is a flexible connection in the form of a tube 86, preferably having a 360 begl 88 formed therein. The lower end of the tube is connected to a second fixture 90 threaded into a portion of the presser foot 18 of the sewing machine. The presser foot 18 is drilled with passages 92 and 94 (Fig. 2) entering a restricted nozzle comprising a rigid plug 96 threaded into a mounting in the form of a bore in an extremity of the presser foot, the 360 bend 88 in the tube enabling the presser foot to move freely in the direction of feed with the work.

In order to enable each charge of adhesive to be projected into the work at a location where each stitch is completed, according to the present invention, the mounting in the presser foot for the nozzle plug 96 is. spaced along the seam line exactly the length of two stitches from the sewing point in the machine with its outlet directed against the work in line with a perforation in which each stitch has been formed. The nozzle 96 has an opening of an extremely small diameter such as 0.012 to 0.014 of an inch. During the operation of the machine the action noted above takes place, a charge of adhesive being squirted from the nozzle into each stitch directly after it is formed and tightened in the work, providing an extremely durable and secure stitch, the interlocking threads being bonded to each other and to the side walls of the perforation in the work. Also, the continuity provided by the conjunction of the charges adhering to the adjacent faces of the work adds to the security of the seam.

To limit the quantity of adhesive delivered during each operation of the impeller the injecting piston 58 is actuated through adjustable means in the same manner as that disclosed in the prior applications. Briefly, the adjustable means for actuating the piston include an adjustable rod 98 pivotally connected at one end to the arm 56 and at the other end to an oscillating lever 100, carried by a pin 102 rotatably mounted in a portion of the frame. For actuating the arm 56 it is connected by a releasable latch 103 to an arm 104 fixed to the shaft 50, the latch being released from a pin on the arm 56 by engagement of one end of the latch with a stop screw 105 in the manner disclosed in the prior applications. A downwardly extending arm of the lever is connected through a rod 106 to a horizontal lever 107 having a square opening fitting loosely around a square portion of the piston 58 to cause rotation of the piston as the lever is actuated. The piston is provided with an axial passage 108, the upper end of which has a vent 110 entering the outer surface of the piston in a position to register with an adhesive supply port 111 in the charge holder 82. When the lever 106 is rotated it turns the piston toward and from a position where the vent 110 registers with the supply port 111. Rotation of the lever 107 also raises the piston 58 to a predetermined position, providing a delivery chamber 112 for the charge to be injected into the work. Raising the piston 58 is accomplished by the movement of a pair of lugs 114 (see Fig. 3) on the piston moving along cam projections 115 on an adjusting handle 116 secured in adjusted position by a clamp screw 118 passing through a slot in a flange on the charge holder and into threaded engagement with the handle 116. Adjustment of the link 98 causes more or less rotation of the piston 58 to insure proper register of the vent 110 with the adhesive supply port 111 and to change the amount by which the piston is raised from the delivery chamber 112. Adjustment of the position of the handle 116 also increases or decreases the size of the delivery chamber 112 beneath the piston 58 and accordingly controls the quantity of charge therein. Other adjustments, described more fully in the prior applications control the velocity of motion imparted to the hammer 60 by changing the compression of the spring 64 and consequently the velocity of the adhesive charge.

In case it is found desirable to dispense with the use of thread in the machine, it is only necessary to remove the awl 26 and the needle 30 utilizing only the work support and presser foot as step-by-step feeding devices. With the needle and awl removed, the velocity of the cement is increased until it is sufficient to penetrate to the desired location in the materials operated upon without first forming a perforation in a manner explained in the above-noted applications. Even without thread the seam has been found to provide sufficient security of connection between layers of work for many practical purposes.

Certain features of the invention herein disclosed form the subject matter of a divisional application for United States Letters Patent Serial No. 625,695, filed December 3, 1956, relating to a thread seam.

The nature and scope of the invention having been pointed out and particular illustrative constructions, modes of operation and examples having been described, what is claimed is:

l. A machine for uniting multilayer work composed of relatively dense materials, such as shoe leather, said machine having fastener-forming and work-clamping devices including an adhesive impeller, a rigid nozzle connected to the impeller and directed against the work engaging the clamping devices, means including actuating mechanism having a spring-actuated hammer raised by said mechanism and released with an explosive blow for causing the impeller to squirt a charge of molten thermoplastic adhesive from the nozzle with a velocity higher than required to cause it to continue in motion by its own inertia into the work to an interface between the layers, and means for feeding the work step by step, uniform distances to form a seam, in combination with means for causing the hammer to be released while the clamping means grips the work, said releasing means including connections between the impeller actuating mechanism and the feeding means.

2. A multilayer work uniting machine having fastener forming, work clamping and step-by-step feeding devices, including an adhesive impeller, a nozzle connected to the impeller and directed against the work, and means including actuating mechanism for the impeller having a spring-actuated hammer raised by said mechanism and released with an explosive blow for causing the impeller to squirt molten thermoplastic adhesive from the nozzle with 'a velocity higher than required to cause it to continue in motion by its own inertia beyond the nozzle into the work, in combination with driving connections between the impeller mechanism and the feeding devices for actuating the hammer against the impeller once at each step of the feeding devices, and means for adjusting the impeller actuating mechanism to that quantity of adhesive required to reach an interface between work layers and migrate between the layers with a continuous bond.

3. A machine for uniting multilayer work composed of relatively dense materials, such as shoe leather, said machine having fastener-forming and work-clamping devices including an adhesive impeller, a rigid nozzle connected to the impeller and directed against the work engaging the clamping devices, means including actuating mechanism hav'mg a spring-actuated hammer raised by said mechanism and released with an explosive blow for causing the impeller to squirt a charge of molten thermoplastic adhesive from the nozzle with a velocity higher than required to cause it to continue in motion by its own inertia into the work to an interface between the layers, and then to migrate laterally along the interface and means feeding the work step by step uniform distances to form a continuous seam, in combination with means for causing the hammer to be released while the clamping means grips the work, the distances through which the feeding means acts being less than the extent of migration of the adhesive to cause the successive charges to form a conjunction with each other, thereby producing a continuous seam.

4. A machine for uniting multilayers composed of relatively dense materials, such as shoe leather, said machine having work piercing, stitch-forming and work-clamping devices for filling perforations formed by the work piercing devices with compacted thread, said devices including an adhesive impeller, a rigid nozzle connected to the impeller and directed against the work engaging the clamping devices, and means including actuating mechanism having a spring actuated hammer raised by said mechanism and released with an explosive blow for causing the impeller to squirt a charge of molten thermoplastic adhesive from the nozzle with a velocity higher than required to cause it to continue in motion by its own inertia into the work and then to migrate laterally along an interface between the work layers, in combination with means for feeding the work step by step with uniform movements to form a seam, at the ends of which feeding movements the nozzle is directed against the work in line with a thread filled perforation and the distances through which the feeding means acts being less than the extent of migration to cause successive charges to form conjunctions with adjacent charges, thereby producing a continuous bond within the work.

5. A method of uniting layers of relatively dense work, including clamping the imperforate layers together and feeding them step by step relatively to the point of operation, which method comprises squirting a charge of liquefied adhesive with a velocity higher than required to cause it to continue in motion by its own inertia through one layer to an interface between said layers at each feeding movement a forepart portion of the adhesive charge being cooled to a solidifying temperature while the still fluent remainder piles up behind the forepart of the charge to form an enlargement.

6. A method of uniting layers of relatively dense work, including clamping the layers together and feeding them step by step relatively to the point of operation, which method comprises squirting a charge of heated thermoplastic adhesive with a velocity higher than required to cause it to continue in motion by its own inertia through one layer to an interface between said layers at each feeding movement, a forepart portion of the adhesive charge migrating between the layers into conjunction with adjacent charges and cooling to a solidifying temperature while the still fluent remainder of the adhesive charge piles up behind the forepart portion to form an enlargement.

7. A method of uniting layers of relatively dense work, including clamping together and feeding them step by step relatively to the point of operation, forming a series of perforations passing through one of said layers and into another and inserting loops of thread within said perforations, which method comprises squirting a charge of heated thermoplastic adhesive with a velocity higher than required to cause it to continue in motion by its own inertia to an interface between layers at each feeding movement, a forepart portion of the adhesive charge migrating between the layers into conjunction with an adjacent charge to bond the loops of thread to the layers and to connect the charges of adhesive in adjacent perforations 'and cooling the forepart of the charge to a solidifying temperature while the still fluent remainder of the adhesive charge piles up behind the forepart portion to form an enlargement.

8. A method of sewing layers of work with a lockstitch seam, which includes clamping together and feeding the layers step by step relatively to the point of operation, forming a series of perforations passing through said layers, passing loops of thread from one side of the work through said perforations to the other side, inserting a loop of another thread into each projecting loop of the first mentioned thread and drawing the loops of the second mentioned thread into the work to form a lockstitch seam, which method comprises squirting a charge of adhesive with a velocity higher than required to cause it to continue in motion by its own inertia through one layer to an interface between layers and beyond the point of interlocking engagement between the loops of thread at each feeding movement of the work with a portion of each charge migrating between the layers into conjunction with an adjacent charge of adhesive to bond the thread within the perforations to the work and to connect the charges of adhesive in the perforations.

References Cited in the file of this patent UNITED STATES PATENTS 1,278,099 Brackett Sept. 10, 1918 1,513,197 Sundean Oct. 28, 1924 1,893,789 Thayer Jan. 10, 1933 2,020,300 Cundall Nov. 12, 1935 2,087,244 Corn July 20, 1937 2,142,733 Movsesian Jan. 3, 1939 2,144,154 Hockman Jan. 17, 1939 2,189,067 Hlavaty Feb. 6, 1940 2,271,611 Ashworth Feb. 3, 1942 2,346,246 Ashworth Apr. 11, 1944 2,418,169 Fredericksen Apr. 1, 1947 2,778,530 Sillars Jan. 22, 1957 FOREIGN PATENTS 649,390 Germany Aug. 21, 1937 

